Readme :Seiko 6309-7040 & 6309-7049 both are successors of Vintage Seiko 6105. The 6309 watch cases have been produced in two or more different styles. The case had been slightly changed from big cushion into slimmed down version. Therefore, each style may have little difference, such as spring-bar-tip-hole dia. & hole-to-case distance. Our 6309 watch band have been tested can fit in a few 6309 models during production period however it may not fit all 6309 models. Suggestion:Our 6039 watch band comes with a pair of Dia. 2.5mm Fat spring bars. If you cannot install successfully, please try to change spring bars with diameter less than 2.5mm, eg. 1.78mm or send us your inquiry.